9. The switch in the circuit of Fig. 8.55 has been closed a ridiculously long time before suddenly being thrown open at t = 0. (a) Obtain expressions for i, and v in the circuit of Fig. 8.55 which are valid for all ≥ 0. (b) Calculate i(t) and 310 www CHAPTER 8 BASIC RL AND RC CIRCUITS v(1) at the instant just prior to the switch opening, at the instant just switch opening, and at t = 470 µs. 10 Ω 25 2 10 V FIGURE 8.55 7+1=0 50 Ω 40 mH

Fig: 1